Switchable tandem memory magneto-optic display

Abstract

A magneto-optic display in which two closely spaced parallel memory chips are mounted together in a projection or direct viewing display device. Light passes through the chips in tandem, but the information on either one of the chips can be separately selected and displayed with no trace of the information on the other chip appearing in the display. An additional polarizer is placed between the two memory chips and is capable of rotating into various predetermined positions to select the desired display. The switching polarizer is electromechanically driven to provide rapid switching between displays. In another mode of operation, the images stored on both chips can be combined in a single display. This display makes it possible to view a steady unblinking image on one chip while the next updated image for viewing is being invisibly written on the other chip. It is also possible to retain both the last and next-to-last images in a sequence of images, but occasionally referring back to the previous one. Three chip embodiments are shown capable of full-color display.

Wherefore, having thus described my invention, I claim: 
     
       1. A magneto-optic display for positioning in a beam of light comprising, in sequence: (a) first means for polarizing light passing therethrough in a first axial orientation;   (b) first magneto-optic chip means for rotating light passing therethrough by Faraday rotation in addressible areas according to a first desired display image;   (c) first adjustable means for polarizing light passing therethrough in a variable axial orientation;   (d) second magneto-optic chip means for rotating light passing therethrough by Faraday rotation in addressible areas according to a second desired display image;   (e) second means for polarizing light passing therethrough in a second axial orientation; and further comprising,   (f) means operably connected to said first adjustable polarization means for selectively changing the axis of polarization thereof.   
     
     
       2. The magneto-optic display of claim 1 and additionally comprising: a relay lens disposed between said first and second magneto-optic chips for focusing the image in the plane of said first magneto-optic chip on said second magneto-optic chip.   
     
     
       3. The magneto-optic display of claim 1 and additionally comprising, in sequence, following said second magneto-optic chip: (a) second adjustable means for polarizing light passing therethrough in a variable axial orientation;   (b) third magneto-optic chip means for rotating light passing therethrough by Faraday rotation in addressible areas according to a third desired display image; and further comprising,   (c) means operably connected to said second adjustable polarization means for selectively changing the axis of polarization thereof.   
     
     
       4. The magneto-optic display of claim 3 and additionally comprising: a first relay lens disposed between said first and second magneto-optic chips for focusing the image in the plane of said first magneto-optic chip on said second magneto-optic chip.   
     
     
       5. The magneto-optic display of claim 3 or claim 4 and additionally comprising: a second relay lens disposed between said second and third magneto-optic chips for focusing the image in the plane of said second magneto-optic chip on said third magneto-optic chip.   
     
     
       6. The magneto-optic display of claim 3 wherein: said means for selectively changing said first and second polarization means is a common means adapted to change said first and second polarization means simultaneously.   
     
     
       7. The magneto-optic display of claim 6 wherein: said first and second polarization means and said first and second adjustable polarization means have their polarization axes oriented such that said first and second adjustable polarization means are movable between a first position where only the display of said first magneto-optic chip is viewable, a second position where only the display of said second magneto-optic chip is viewable, and a third position where only the display of said third magneto-optic chip is viewable.   
     
     
       8. The magneto-optic display of claim 7 wherein: said first and second polarization means and said first and second adjustable polarization means comprise discs rotatable on a common shaft wherein said discs for said first and second polarization means have a common polarization axis throughout and said discs for said first and second adjustable polarization means are comprised of segments having different polarization axes.   
     
     
       9. The magneto-optic display of claim 7 and additionally comprising: means for sequentially moving said first and second adjustable polarization means between said first, second, and third positions.   
     
     
       10. The magneto-optic display of claim 9 and additionally comprising: full-color means operably connected to said common shaft and disposed prior to said first magneto-optic chip means; said full-color means limiting light passing to said chip means to a first primary color during said first position, to a second primary color during said second position, and to a third primary color in said third position so that a full-color display is viewable.   
     
     
       11. The magneto-optic display of claim 10 wherein: said first and second polarization means, said first and second adjustable polarization means, and said light limiting means comprise discs rotating on a common driven shaft.   
     
     
       12. The magneto-optic display of claim 10 wherein: (a) said light limiting means comprises three selectable light sources producing the three primary colors, respectively;   (b) said first and second adjustable polarization means comprise solid state adjustable polarizers; and further comprising,   (c) control circuit means operably connected to drive said light sources and said solid state adjustable polarizers.   
     
     
       13. The magneto-optic display of claim 10 in which said full-color means is a primary color filter disc having an equal sector area for each of said first, second, and third primary colors. 
     
     
       14. The magneto-optic display of claim 13 in which said full-color means includes a light chopper means to increase flicker frequency above the flicker fusion point of a human viewer of the full-color display. 
     
     
       15. The magneto-optic display of claim 3 and additionally comprising: (a) in sequence, preceding said first means, (1) a light source,   (2) a heat filter, and   (3) a focus lens disposed between said heat filter and said first means for focusing said light source on said first means; and     (b) in sequence, following said third magneto-optic chip means, (1) a projection lens disposed between said third magneto-optic chip means and said second means, and   (2) a viewing surface spaced-apart from said second means and adapted to display an image focused by said projection lens thereon.     
     
     
       16. The magneto-optic display of claim 15 in which said first, second and third magneto-optic chip means are positioned within the focal range of said focus lens.